Brush mechanisms



Jan. 10, 1967 G. w. LlTZ BRUSH MECHANISMS 2 Sheets-Sheet 1 Filed Sept. 19, 1963 INVENTOR GEMGE 14 4/72,

ATTORNEKS Jan. 10, 1967 (5. w. LITZ 3,297,393

' BRUSH MECHANISMS Filed Sept. 19, 1965 2 Sheets-Sheet 2 llllllllllmm INVENTOR GEORGE 14 .L/ 72 Mi a;

ATTORNEXfi United States Patent 3,297,893 BRUSH MECHANISMS George W. Litz, Litz.Co., Rte. 2,

White Pine, Tenn. 37890 Filed Sept. 19, 1963, Ser. No. 310,041

- -7 Claims. (Cl. 310-246) This invention relates generally to brush mechanisms and more specifically to brush mechanisms for use in electrical apparatus including spring means for biasing a brush into contact witha moving membensuch as a commutator. Y

It is conventional. practice to provide spring means in brushmechanisms to urge the brush into contact with a moving member in electric motors or generators. It is important that the brush gear aga inst the moving fmernher with uniform pressure to obtain eflicient: operation of the electrical apparatus. In order to accomplish this, steel springs are usually employed for urging the brush into engagementwith the moving member.

The brush holder is usuallyformed of a metal having low electrical resistance and is provided with shunt means to carry current between a main. lead and the brush. In some instances, the current may be permitted to flow through the brush holder between the main lead and the brush.

During operation of the electrical apparatus, the flow of current may be caused to pass through the springs.

This may be caused by various things; for example, a

shunt may become corroded or broken thereby causing high resistance to flow of current therethrough. The current would then seek a path of less resistance, which in many instances would be the spring. The flow of current through the spring causes the spring to become heated, and frequently causes annealing of the spring metal. The resulting annealing action reduces the spring tension and thus reduces the brush pressure on the moving member. This condition is undesirable and could result in arcing at the point of contact of the brush with the moving member thereby causing serious damage to the brush holder. In many instances, portions of the brush holder have actually melted, thus causing serious damage to the entire electrical apparatus.

It is, therefore, an object of this invention to provide a brush mechanism which overcomes this problem.

It is another object of this invention to provide a brush mechanism having adjustable spring means for maintaining contact of the brushes and having means to insulate the spring means from the brushes.

These and other objects of the invention may be accomplished according to one embodiment of the invention wherein the brush mechanism comprises a brush holder having a pair of insulated studs for mounting the brush mechanism in the electrical apparatus. Springs are adjustably secured to the brush holder and positioned to engage the brushes to urge them against a moving member of an electric motor or generator. The end of the spring engaging the brush is provided with insulation so as to insulate the spring from the brush. The insulation is molded onto the spring in one embodiment. In another embodiment, the insulation may be applied in liquid form by spraying the end of the spring and then baking the insulation. In still a further embodiment, the end of the spring may be wrapped with suitable material such as fiberglass. This material is then coated in the deisred position when with an insulating material in liquid form and baked to a solid state. These embodiments of the invention are illustrated in the accompanying drawings, in which:

FIG. 1 is .a top plan view of the brush holder for a pair of brushes having coil springs mounted thereon for engagement with the brushes;

FIG. 2 is .a side elevational view thereof;

' FIG. 3 isa sectional view, taken on line 3-3 in FIG. 1; V FIG. 4isa partial sectional view of one form of the insulated spring; p

' FIG. 5 is atop plan view of a further modified form :of the invention; 7

FIG. 6 is a partial sectional view taken on line 6-6 in FIG. 5; and FIG. 7 is a sectional view, taken on line 77 in FIG. 5.

The brush mechanism. 10 includes a brush holder 12 formed of a suitable metal having a low electrical resistance, such as bronze. The brush holder 12, in the illustrated embodiment, is provided with a pair of studs 14, shown in broken lines in FIGS. 1 and 2, and extending in insulating posts 16. The brush holder 12 is supported in the electrical apparatus by connecting the studs 14 t0 the frame of the electrical apparatus with suitable means. The studs 14 are secured in apertures in the brush holder 12 and held therein securely by a pin 15 extending through the apertures in the brush holder 12 and the studs 14. The insulating material of the posts 16 insulates the brush holder 12 from the frame of the apparatus to which it is connected. In the preferred embodiment of the invention, the posts 16 are molded 0n the studs 14.

Power may be supplied to or delivered from, as the case may be, by a lead line 17 secured to the brush holder 12. Shunt wires, not shown, may be secured to the brush holder 12 by bolts 18 and connected to the brushes. If the brush holder 12 is used in an electric motor, current would be supplied through lead line 17 t0 the brush holder. Shunt wires would carry the current to the brushes from the brush holder 12.

The brush holder 12 includes a chamber 19 in which brushes B, shown in broken lines in FIG. 3, are slidably supported. In the illustrated embodiment, the chamber 19 is adapted to accommodate two brushes; however, only one brush may be used if so desired. A spring 20 is provided to urge resiliently each of the brushes B into contact with the movable member of the electrical apparatus.

Each spring 20 is mounted on the brush holder with an end 21 overlying the chamber 19. In the illustrated embodiment, the springs 20 are coil springs. Leaf springs or other suitable forms of springs may be utilized if so desired. Each spring 20, in this embodiment, is supported on the brush holder 12 on a spindle 22 rotatably supported in a bore in the brush holder body. The spindles 22 are slotted to receive the coiled ends of the springs 20, as best shown in FIG. 3. Each spindle 22 is provided with a groove 23 in its end so that the tension of the associated spring 20 may be adjusted by engaging the groove 23 with a screw driver and rotating the spindle until the desired tension of the spring is obtained. Set screws 24 are provided to secure the spindles 22 the springs 20 have been tensioned properly.

The ends 21 of the springs 20 overlying the chamber 19 are covered with suitable insulating material 26 to insulate the springs from the brushes by encasing the bearing portions of the springs with suitable insulation. In one embodiment of the invention, the insulation 26 is molded on each spring end 21 and may be formed of a suitable material, such as fibgerglass. In this manner, it will be understood that the springs will bear against the brushes to hold them in contact with the movable member of the electrical apparatus for good connection therewith, but the springs will be insulated therefrom so that current will not flow through the springs, thereby heating the springs and causing the tension of the springs to decrease.

A further embodiment of the invention is illustrated in FIG. 4 wherein the insulation 27 is formed on the end of a spring 28, by coating the end of the spring with insulating material in liquid form, by spraying or dipping, and then baking the material to a solidified state.

Still a further embodiment of the invention is illustrated in FIGS. 5, 6 and 7 of the drawings. This embodiment may be utilized with smaller springs for use in smaller electrical apparatus when less pressure is required to maintain the brush against the movable member. The brush holder 30, of this embodiment, is smaller and is illustrated with a single spring 32. The spring 32 is secured adjustably to the brush holder by a pin 34 extending through an aperture in the brush holder 30 and having a groove therein to receive the coiled end of the spring as shown in FIG. 7. A nut 35 is provided to secure the pin 34 in place. A washer 36 and cotter pin 38, or other suitable means, maintain the spring 32 on the pin 34. The tension of the spring 32 maybe varied by loosening the nut 35 and rotating the pin 34.

The outer end of the spring 32 is insulated and is positioned over a brush chamber 42 in the brush holder 30. Insulation is applied to the outer end in still a different manner, in this embodiment of the invention, as shown in FIG. 6. Flexible material 44, such as fiberglass cloth, may first be Wrapped about the end of the spring 32 and then the material is coated with a suitable dielectric material .46 and baked to a hardened solidified state. In this manner, sufiicient insulation is provided on the end of the spring 32 to insulate it from the brush which it contacts.

Many forms of springs may be utilized for maintaining a brush in proper contact with the movable member of the electrical apparatus. The provision of insulation on the portion of the spring contacting the brush may be applied to various springs in any of the manners illustrated above.

The brush may be moved against the commutator in a conventional manner which is in turn urged by spring .means. In this instance the end of the spring engaging the movable member or brush may be insulated in any of the manners described above.

It will thus be understood that the invention provides a novel brush mechanism wherein the resilient means urging the brush into contact with the movable electrical member is insulated properly therefrom so that the resilient means will not become heated and thereby lose its tension. The invention accomplishes this in a very economical and practical manner so as to become commercially feasible.

This invention may also be utilized with springs which are used to urge electrical conductors into engagement with stationary contacts.

While the invention has been illustrated and described in certain embodiments, it is to be understood that changes and modifications can be made therein without departing from the invention as set forth in the claims.

I claim:

1. A brush mechanism for dynamoelectric machines comprising a holder having a chamber adapted to support at least one "brush therein, resilient means mounted on said holder, said resilient means having a portion thereof in position to engage said brush for urging said brush into contact with a moving member of said machine, and insulation encasing said engaging portion of the resilient means and secured to said portion in position to insulate said resilient means from said brush to prevent current from passing through said resilient means.

2. A brush mechanism for dynamoelectric machines comprising a holder having a chamber adapted to support at least one brush therein, resilient means mounted on said holder, said resilient means having a portion thereof in position to engage said brush for urging said brush into contact with a moving member of said machine, means for adjusting tension of said resilient means, insulation secured to said portion to insulate said resilient means from said brush to prevent current from passing through said resilient means, and said insulation comprising a layer of dielectric material encasing said portion of the resilient means.

3. A brush mechanism for dynamoelectric machines comprising a holder having a chamber adapted to support at least one brush therein, resilient means mounted on said holder, said resilient means having a portion thereof in position to engage said brush for urging said brush into contact with a moving member of said machine, means for adjusting tension of said resilient means, insulation secured to said portion to insulate said resilient means from said brush to prevent. current from passing through said resilient means, said insulation comprising a plurality of layers of flexible dielectric fabric extending around the bearing portion of the resilient means and forming a layer of dielectric material thereon.

4. A brush mechanism for dynamoelectric machines comprising a holder having a chamber adapted to support at least one brush therein, at least one coil spring mounted on said holder, an elongated member rotatably supported in said holder, said spring having its coiled end secured to said elongated member, said elongated member being adapted to be rotated to vary the tension of said spring, said elongated member having an abutment on one end thereof and a nut on the opposite end thereof in clamping relation with a portion of the holder for locking said elongated member against rotation, said spring having a portion thereof in position to engage a brush held in said brush chamber.

5. A brush mechanism for dynamoelectric machines comprising a holder, said holder having an elongated chamber adjacent one side thereof adapted to support two brushes therein, a pair of coil springs mounted on said holder, a first spindle rotatably mounted in said holder in spaced relation to said chamber, one of said pair of coil springs having its coiled end secured to said first spindle and having its other end overlying said chamber in position to engage a brush supported therein, a second spindle rotatably mounted in said holder in spaced relation to said chamber, the other of said pair of coil springs having its coiled end secured to said second spindle and having its other end overlying said chamber in position to engage a further brush in said chamber, said spindles being adapted to be rotated to vary the tension of said coil springs, means for locking said spindles against rotation, insulated studs on said holder adapted to be connected to said dynamoelectric machine, the end of each of said coil springs being provided with insulation, said insulation encasing completely the end of each of said coil springs in position to engage a brush to insulate each of said coil springs from said brushes to prevent current from flowing through said coil springs.

6 A brush mechanism according to claim 1, wherein the insulation encases the bearing portion of the resilient means and adheres thereto.

7. A brush mechanism according to claim 1, wherein the resilient means comprises a coiled spring having an end portion forming the bearing portion of the resilient means and which end portion is encased completely in brush.

References Cited by the Examiner UNITED STATES PATENTS Flower 310246 5 Dean 310241 MacCutcheon 310246 Klinger et a1 310246 Baldwin 310--239 6 2,488,788 11/ 1949 Weilbrecher 310246 2,842,693 7/1958 Tubbs 310246 X 2,900,540 8/ 1959 Gartner et a1 310-246 3,158,772 11/ 1964 Krellner 310246 MILTON O. HIRSHFIELD, Primary Examiner. O. L. RADER, Examiner.

C. W. DAWSON, D. F. DUGGAN, Assistant Examiners. 

5. A BRUSH MECHANISM FOR DYNAMOELECTRIC MACHINES COMPRISING A HOLDER, SAID HOLDER HAVING AN ELONGATED CHAMBER ADJACENT ONE SIDE THEREOF ADAPTED TO SUPPORT TWO BRUSHES THEREIN, A PAIR OF COIL SPRINGS MOUNTED ON SAID HOLDER, A FIRST SPINDLE ROTATABLY MOUNTED IN SAID HOLDER IN SPACED RELATION TO SAID CHAMBER, ONE OF SAID PAIR OF COIL SPRINGS HAVING ITS COILED END SECURED TO SAID FIRST SPINDLE AND HAVING ITS OTHER END OVERLYING SAID CHAMBER IN POSITION TO ENGAGE A BRUSH SUPPORTED THEREIN, A SECOND SPINDLE ROTATABLY MOUNTED IN SAID HOLDER IN SPACED RELATION TO SAID CHAMBER, THE OTHER OF SAID PAIR OF COIL SPRINGS HAVING ITS COILED END SECURED TO SAID SECOND SPINDLE AND HAVING ITS OTHER END OVERLYING SAID CHAMBER IN POSITION TO ENGAGE A FURTHER BRUSH IN SAID CHAMBER, SAID SPINDLES BEING ADAPTED TO BE ROTAED TO VARY THE TENSION OF SAID COIL SPRINGS, MEANS FOR LOCKING SAID SPINDLES AGAINST ROTATION, INSULATED STUDS ON SAID HOLDER ADAPTED TO BE CONNECTED TO SAID DYNAMOELECTRIC MACHINE, THE END OF EACH OF SAID COIL SPRINGS BEING PROVIDED WITH INSULATION, SAID INSULATION ENCASING COMPLETELY THE END OF EACH OF SAID COIL SPRINGS IN POSITION TO ENGAGE A BRUSH TO INSULATE EACH OF SAID COIL SPRINGS FROM SAID BRUSHES TO PREVENT CURRENT FROM FLOWING THROUGH SAID COIL SPRINGS. 